The two accidents we analysed in the other sections (Metrolink accident at Chastworth and theHudson river midair collision) have in common the fact that one of the people responsible for the security of the passengers was engaged in a private communication at the time of the crash. In the first case the train driver was texting, in the second the air traffic controller was making a phone conversation with a colleague.
The case of the air traffic controller can maybe help explain what happened on the train. The controller handed off the Piper to the next control centre at Newark and asked the pilot to contact the Newark control on a different frequency. From that moment he had in a certain sense finished his task with that aircraft. He probably had a sense of closure of the activity regarding the Piper plane, and did not have anything else urgent on his screen and therefore heresumed his call with a friend. He therefore fell into a typical mechanism associated with personal phone calls from the workplace : calls or other forms of private contact are inserted in moments when there is a feeling that a task has been achieved. There is a cycle of activity and when there is a sense that there is a break in the cycle either because the task is completed or because the person has to wait for the next cycle of activity to begin, then a text is sent or a call made.
We can make the hypothesis that train engineer driving the Metrolink also erroneously had had a sense of having done the necessary activities involved in leaving the station and starting a 6 minute uninterrupted trail to the next station. Something may have given him the impression that all was clear and that he could relax his attention. He may have thought that he had ample time to send a few messages before he had to focus again.
Using personal calls as break fillers, small rewards for tasks accomplished, or ways to counteract the dullness of an activity is very common. People don’t just drop what they are doing to suddenly send an SMS or an email, but wait for one of these moments (unless they have to interrupt what they are doing to answer a call but in that case they are not the initiators of the action). The sense of closure or waiting for the next task depends on the nature of the activity as well as personal disposition. Different activities have different cycles and therefore down moments or closures can have different frequencies. Clearly there are also limitations in people’s attention cycles.
When writing we can feel that the end of a page or paragraph is an achievement that closes a cycle of concentration and that can be rewarded by a small break of attention. This break can be occupied by going to have a coffee, reading email, reading something or sending an SMS. Similarly when doing any manual activity there are points of closure before a new set of actions start (e.g. waiting for a surface to dry before polishing it) that can also be used as breaks. There are also many activities that are highly predictable and skilled workers know that at certain points there will be some prolonged moments of waiting. Often they will also be able to predict how long the wait will be. For instance in manufacturing people who control processes often know exactly how long it will take for a process they initiate to have an effect. In that time they may just be waiting for things to happen. These are typically moments in which a parallel activity may take place, sometimes a self gratifying activity. A few years ago this could have been a cigarette now it could be an SMS.
These parallel activities often are not aimed at relaxation but on the contrary as stimulations to reactivate attention, emotional drive, energy. If we look at the type of actions most often associated with breaks (having a coffee, a cigarette or a snack) we tend to find a group of stimulants : caffeine, nicotine, glucose. SMS, emails and other communication channels could be playing the same role, their high emotional nature may be acting as a stimulant that people are using as a self gratification but also as a way to maintain high levels of vigilance. Maintaining alertness and vigilance is a cognitively demanding task as many studies have shown : underload (boring tasks that involve a lot of waiting and routine) can be as demanding as overload (where there is too much information to process) and just as risky in terms of potential decrease of attention.
Accidents may well occur when operators or drivers mistakenly feel that they have finished a task or cycle and are waiting for the next event to act upon, or when they have miscalculated the latency between the two cycles. It is well possible that in both accidents the operators released their attention too early, estimating that their cycle was done and they had time for a parallel activity before refocusing. There may also be a problem with the level of engagement that the communication activities require: it may be the case that the conversations (textual or oral) actually took longer or required more attention than the operators estimated. This could be the case with many communication channels as they may require more mental processing and emotional involvement than people think, therefore pulling them into a longer defocusing than expected.
The question that both tragedies raise however, is why so many human lives should rely on such fragile processes. How is it possible that a lapse of attention of one individual for such a short length of time can cause so many deaths? The context of both accidents ( a one track rail system and a densely trafficked unregulated airspace) creates the highly risky conditions in which diminished attention becomes fatal.